Method of producing mercaptans



11.5. Cl. 260-609 8 Claims ABSTRACT OF THE DISCLOSURE A method of producing a mercaptan by reacting hydrogen sulfide with an aliphatic olefin in an anhydrous liquid phase in the presence of a peroxyester having the formula II R.00R2

in which R is a member selected from the group consisting of alkyls of 1-10 carbon atoms and benzyl, and R is t-butyl.

The present invention relates to a method of producing primary or secondary mercaptans by adding hydrogen sulfide directly to olefins using organic peroxyesters as a catalyst.

The previous methods of synthesizing mercaptans by radical addition of hydrogen sulfide to olefins include a process for using a'-azodiisobutyronitrile or di-t-butylperoxide together with water (US. Patent No. 2,865,965 (1958)); a process for using anhydrous ferric chloride together with cumenehydroperoxide or methylet-hylketone peroxide (US. Patent No. 2,925,443 (1960)); a process for using di-t-butylperoxide and metal powder (US. Patent No. 3,045,053 (1962)); and a process for using azonitrile as catalysts. These processes, however, give low yields and those employing organic peroxides have the further disadvantage of requiring other reaction additives.

The present invention consists in a method of producing mercaptans by adding hydrogen sulfide to an aliphatic olefin characterized in that the addition is effected in the presence of a peroxyester having the general formula wherein R is a member selected from the group consisting of alkyls of 1-10 carbons and benzyl, and R is t butyl; said addition being conducted in an anhydrous liquid phase.

An object of the present invention is to provide an advantageous method of producing mercaptans wherein the reaction is efiected in an anhydrous liquid phase to produce mercaptans always in a higher yield than byproduct sulfides. Non-reacted hydrogen sulfide is recovered by difference of temperature between a recovery bomb, recovered hydrogen sulfide being recycled.

The olefins employed in the process of this invention are aliphatic olefins of 350 carbon atoms, preferably having terminal unsaturation such as propylene, pentene, l-octene, diisobutylene, l-decene, l-dodecene, l-tetradecene, l-pentadecene, l-hexadecene, 1-octadecene,tetracontene etc.

As the peroxyester, mention may be made of t-butylperoxypivalate, t-butyl-peroxyisobutylate, t-butyl-peroxylaurate, and t-butyl-peroxybenzoate.

The above-described peroxyesters are added in an amount of 1 to by weight based on the starting ole- 1- rd States Patent 0" 3,459,809 Patented Aug. 5, 1969 fins, preferably 2 to 5% by weight. In less than 1%, the activity of catalyst is poor and in more than 10% the yield of by-product disulfide increases.

The mole ratio of hydrogen sulfide to olefin is preferably about 4/1 to 15/1 and more particularly 6/1 to 10/1. When this ratio is less than about 4/ 1, formation of by-products such as dialkylsulfide, dialkyldisulfide, olefin polymers etc. increases. Ratios greater than about 15/1 are not preferred since mercaptan yield is not improved and economics of the process are efiected because of reactor and hydrogen sulfide recovery requirements.

The reaction must be eifected in liquid phase. Accordingly it is necessary that hydrogen sulfide be maintained always in an excess amount, as above described, in the reaction mixture and is in a liquid state. Otherwise, mercaptans produced in the reaction react with nonreacted olefin to produce by-product alkylsulfides with corresponding decrease in yield of mercaptans. The excess of hydrogen sulfide acts as the sol-vent for the produced mercaptan and prevents contact of olefin with mercaptan.

The reaction temperature appears to be critical for each peroxyester employed, but in all cases will range between about 50 to 130 C. For example, when using t-butyl-peroxypivalate, the reaction is preferably effected at a temperature between 50 to C. At a temperature of less than 50 C., the decomposition of peroxyester is considerably slower so that it is difficult for the reaction to proceed. Furthermore, at a temperature of more than 130 C., the by-products such as dialkylsulfide, dialkyldisulfide etc. increase.

The pressure, when hydrogen sulfide and olefin are reacted in the presence of the above-described peroxyesters, is one sufiicient to liquefy hydrogen sulfide and although the value is influenced by hydrogen sulfide fed and the reaction temperature, it is generally about 20 kg./crn. to 120 kg./cm.

The reaction time is preferably 2 to 15 hours. In less than 2 hours, the reaction proceeds only slightly and the yield of mercaptan is poor, while at reaction times greater than 15 hours, the yield of by-products increases.

The process for recovering non-reacted hydrogen sulfide utilizes the difference of temperature between the reaction vessel and a bomb employed for recovering hydrogen sulfide. More than of the excess hydrogen sulfide used can be recovered by maintaining the temperature of the recovering bomb 50 to C. preferably 80 to 90 C. lower than that of the reaction vessel. The recovered hydrogen sulfide contains a very small amount of impurities formed by decomposition of peroxide so that is can be recycled and used repeatedly for the reaction as such. Accordingly, when this process is practiced, a special apparatus for recovering hydrogen sulfide is not necessary.

After the reaction is complete and the excess hydrogen sulfide recovered as above described, the reaction products are treated with an amine to decompose any remaining peroxyester, and the mercaptan recovered as by distillation.

The following examples are given in illustration of this invention and are not intended as limitations thereof.

EXAMPLE 1 168 g. of dodecene-l and 15 g. of t-butyl-peroxypivalate were introduced into a 500 ml. autoclave, which was purged with nitrogen and to which was then added 204 g. of hydrogen sulfide. The resulting mixture was stirred at 60 C. for 5 hours. In this case, the pressure was 30 to 35 kg./cm. After completion of the reaction, the stirring was stopped and the reaction vessel at such temperature was connected by a lead pipe with a 300 ml. bomb cooled to 5 C. and the cock of the reaction vessel was opened. Then the temperature of the reaction vessel was raised to 90 C. to transfer hydrogen sulfide from the reaction vessel to the bomb rapidly. 155 g. of hydrogen sulfide, representing 91% of the excess, was recovered. To the reaction product were added 5 g. of ethylenediamine to decompose the non-decomposed peroxyester, and then a distillation was effected to obtain 154 g. of the primary dodecylmercaptan and 30 g. of dodecylsulfide. The yield of mercaptan was 76% EXAMPLE 2 In this example the amount of t-butyl-peroxypivalate added was varied. Namely, the reactions were effected in the same manner as described in Example 1, except that t-butyl peroxypivalate was used in amounts of 5 g. and 10 g. to obtain yields of dodecylmercaptan of 59% and 70% respectively as shown in Table 1. From the result of Table 1, it is apparent that as the amount of t-butyl-peroxypivalate increases, the yield is improved.

TAB LE 1 Yield of dodecylmcrcaptan Amount Pressure Amount of t-butylof sulfid kgJem. peroxypivalate (g.) (G.) Percent (g.)

EXAMPLE 3 In this example the amount of hydrogen sulfide added was varied. Namely, the reaction was effected in the same manner as described in Example 1, except that hydrogen sulfide was used in amounts of 136 g. and 238 g. to obtain yields of dodecylrnercaptan of 55% and 76% respectively as shown in Table 2.

TABLE 2 Yield of dodecylmcrcaptan Amount Pressure Amount of hydrogen i sulfide kgJcm. sulfide (g.) (G) Percent (g.)

From the above table, it appears preferable to use more than 204 g. of hydrogen sulfide (mole ratio to the olefin of 6).

EXAMPLE 4 In this example the reaction time was varied. Namely, the reaction was effected in the same manner as described in Example 1, except that t-butyl-peroxypivalate was used in an amount of 5 g. and the reaction times were 5, and hours to obtain the yields of dodecylmercaptan of 59, 66 and 59% respectively as shown in Table 3.

TABLE 3 Yield of dodecyl- Reaction mercaptan Amount of time sulfide Pressure, (l1r.) G. Percent (g.) kgJcm.

From the results of Table 3, it appears that at the conditions of Example 3, a reaction time of 10 hours is preferable.

EXAMPLE 5 In this example, the reaction temperature was varied. Namely the reaction was elfected in the same manner as described in Example 1, except that t-butyl-peroxypivalate was used in an amount of 5 g. the reaction time was 10 hours and the reaction temperatures were 50, 60, 70, 80 and 100 C. to obtain the yields of dodecylmercaptan of 4 29, 66, 77, 73 and 68% respectivey as shown in Table 4.

TABLE 4 Yield of dodecyl- Reaction rnercaptan Amount of temperature sulfide Pressure, C.) G. Percent (g.) kg./cm.

As seen from the above table, the best result was obtained at the reaction temperature of 70 C.

EXAMPLE 6 EXAMPLE 7 168 g. of dodecene-l and 10 g. of t-butyl-peroxyacetate were introduced into a 500 ml. of autoclave, which was purged with nitrogen and into which was fed 204 g. of hydrogen sulfide. The resulting mixture was reacted at a temperature of 100 C. for 10 hours. In this case, the pressure was 61 kg./cm. The yield of dodecylmercaptan was 41% and didodecylsulfide was 21 g.

EXAMPLE 8 168 g. of dodecene-l and 10 g. of t-butyl-peroxy-isopropylcarbonate were introduced into a 500 ml. autoclave, which was purged with nitrogen and to which was then fed 204 g. of hydrogen sulfide. The resulting mixture was stirred at C. for 10 hours. The pressure was 45 kg./cm. As the result, the yield of the primary dodecylmercaptan was 33 and the yield of didodecylsulfide was 26 g.

EXAMPLE 9 168 g. of dodecene-l and 10 g. of t-butyl-peroxylaurate were introduced into a 500 ml. autoclave, which was purged with nitrogen and to which was then fed 204 g. of hydrogen sulfide. The resulting mixture was reacted at C. for 10 hours. The pressure was 58 kg./cm. The yield of dodecylmercaptan was 35% and the yield of didodecylsulfide was 30 g.

EXAMPLE 10 112 g. of octene-l and 5 g. of t-butyl-peroxypivalate were introduced into a 500 ml. autoclave, which was purged with nitrogen and to which was then fed 204 g. of hydrogen sulfide. The resulting mixture was reacted at 70 C. for 10 hours. The pressure was 40 kg./cm. The yield of the primary octylmercaptan was 70% and the yield of dioctylsulfide was 18 g.

EXAMPLE 11 In this example, the reaction was etfected in the same manner as described in Example 10, except that 140 g. of decene-l were used instead of octene-l to obtain a yield of the primary decylmercaptan of 72% and a yield of didecylsulfide was 23 g.

EXAMPLE 12 In this example, the reaction was effected in the same manner as described in Example 10, except that diisobutylene was used instead of octene-l to obtain a yield of the primary and secondary octylmercaptans of 65% and a yield of dioctylsulfide of 20 g.

EXAMPLE 13 The reaction of this example was effected at 70 C.

6 dodecene, l-tetradecene, l-pentadecene, l-hexadecene, 1- octadecene and tetracontene.

3. The method according to claim 1 in which the mol ratio of hydrogen sulfide to olefin is about 6/1-10/1. 4. The method according to claim 1 in which said for 9 hours by using 168 g. of dodecene-l, 204 g. of hy- 5 peroxyester is present in an amount of about 2.05.0% drogen sulfide and 7 g. of t-btuyl-peroxypivalate. On combas d o th weight of the olefin, pletion of the reaction, the non-reacted hydrogen sulfide 5. The method according to claim 1 in hi h th was recovered in the same manner as described in EX- a tion time is 2 to hours. ample 1 and used in the reaction repeatedly. About 6 mols 6, Th th d according to l i 1 i hi h th of fresh hydrogen sulfide were added to each repeat ac- 10 tion pressure is about kg./cm. to 120' kg./cm. tion. The reactions were repeated four times and about 7. The method of claim 1 in which said reaction is con- 90% of non-reacted hydrogen su fide s r6d ac ducted in a reaction vessel and nonreacted hydrogen sultime. There was no variation in the yield of mercaptan. fide contained therein is recovered therefrom by main- TABLE 5 Hydrogen sulfide Temperature Amount Excess Recovered Amount of difference Yield of Repeated used for amount amount fresh H in the remercaptan times reaction (g.) (g.) (g.) added (g.) covery 0.) (percent) What we claim is: taining said vessel in communication with a hydrogen 1. The method of producing a mercaptan which consulfide recovery vessel maintained at a temperature of sists essentially of reacting hydrogen sulfide and an alifrom 50120 C. below that maintained in said reaction phatic olefin in an anhydrous liquid phase at a temperavessel, and recycling to said reaction vessel hydrogen sulture of about 50-130 C. in the presence of a peroxyester having the formula fide so recovered.

8. The method according to claim 7 in which the temperature in said recovery vessel is maintained at a temperature of -90 C. below that in said reaction vessel.

References Cited UNITED STATES PATENTS 2,865,965 12/1958 May et al 260609 3,045,053 7/1962 Fond 260-609 CHARLES B. PARKER, Primary Examiner D. R. PHILLIPS, Assistant Examiner US. Cl. X.R. 260-608 

